Hi,

I have a question that I feel has a simple answer, but I do not know. I am looking at my second level results in males and females independently. I have two groups (controls, and experimental group). So far, I have been only comparing male experimental subjects to male controls or female experimental group to female control group. For both of these analyses I used a 1, -1 contrast. However, now I want to see if the effect of the experiemental group (basically just subjects with a certain diagnosis) differs between males and females. I was hoping to be able subtract the two contrasts [(male experimental - male control) - (female experimental - female controls)]. But I cannot figure out how to do this in the second level tab. Does anyone know how I can determine how my experimental group affects male and female connectivity differently?

In my set up i have four groups - male experimental, male controls, female experimental female controls. For experimental males I entered 1 for all the experimental males, 0 for the control males, and NaNs for all the female subjects. I did the other four groups the same way. I do not have a covariate for all of the male/female subjects (inclusive to controls and experimental subjects) because I split it up into four groups this way. I hope this helps you understand my set up. 

I was also considering making a covariate interaction. Alternatively I was consideirng comparing (experimental males - experimental females) to (control males - control females), but I feel like this wouldn't really highlight how the diagnosis impacts sexes differently either. Not exactly sure if these options would be the correct route... I would really like to subtract the contrasts I spoke about in my first paragraph the most, because I feel like that is the most logical.  


I look forward to hearing from you.